Power conversion device

1. A power conversion device comprising: a DC power supply unit; a plurality of power conversion units which are provided in parallel with each other through a DC link portion to convert DC power supplied from the DC power supply unit to AC power and output the AC power; a plurality of semiconductor switch elements each interposed between each of the plurality of power conversion units and the DC power supply unit, each of the plurality of semiconductor switch elements being provided in a forward direction with respect to a flowing direction of a current inherent to the DC power supply from the DC power supply unit to each of the plurality of power conversion units to individually restrict or block the DC power supplied to the each of the plurality of power conversion units; and a control circuit which monitors an occurrence of a short-circuit current occurring in each of the plurality of power conversion units and controls a semiconductor switch element, of the plurality of semiconductor switch elements, connected to a power conversion unit, of the plurality of power conversion units, where the short-circuit current occurs to be turned off to stop the DC power supply to the short-circuited power conversion unit and to electrically disconnect the short-circuited power conversion unit from the DC link portion so as to maintain operations of other remaining power conversion units, of the plurality of power conversion units, where no short-circuit occurs, wherein the control circuit detects the short-circuit current of the power conversion unit based on a decrease in a voltage of a smoothing capacitor installed between the DC link portion and the short-circuited power conversion unit caused by a short-circuited semiconductor switching element constituting a main body of the power conversion unit or an increase in a current flowing into the short-circuited power conversion unit from the DC link portion in accordance with the voltage decrease, and turns off the semiconductor switch element corresponding to the short-circuited power conversion unit.

2. The power conversion device according to claim 1 , wherein each of the plurality of power conversion units is an inverter unit which generates a three-phase AC power.

3. The power conversion device according to claim 1 , wherein each of the plurality of semiconductor switch elements is provided in both a positive electrode side and a negative electrode side of a DC input portion of each of the plurality of power conversion units.

4. The power conversion device according to claim 1 , wherein each of the plurality of semiconductor switching elements is an insulated-gate bipolar transistor (IGBT) having a current sense terminal and an emitter terminal, and the control circuit monitors the occurrence of the short-circuit current by further detecting the current flowing through the current sense terminal of the respective one of the plurality of semiconductor switching elements.

5. The power conversion device according to claim 1 , wherein each of the plurality of semiconductor switching elements is an insulated-gate bipolar transistor (IGBT), and the control circuit monitors the occurrence of the short-circuit current further based on collector voltages of the respective IGBTs.